Photo-electric tube



Patented Jan. 9, 1934 UNITED STATES PATENT @FFECE Claims.

The present invention pertains to a novel photo-electric tube designed especially for use in television apparatus as disclosed in my co-pending application, Serial No. 617,549 filed June 16,

The principal object of the invention is to provide a fine grained, and instantaneously fully developed image on a film, and it will be understood in this connection that the fineness of grain 10 is proportional to the number of current impulses occurring over a given area of the object to be sent. In the television apparatus or system to which this tube pertains, the image is received on a film coated or impregnated with ll an opaque substance which is instantaneously and fully developed by means of electrical discharges passed through the film and varying in intensity according to the emissions from the photo-electric tube at the sending apparatus. It

is contemplated to produce the electrical di charges at a higher frequency than possible with any known mechanical means, and accordingly the current passed through the tube is utilized to determine the frequency of the impulses in the receiving mechanism. This result is accomplished by passing an alternating current through the tube so that interruption is produced by theactivity of the tube while the current flowing therethrough is positive. Frequencies of a very high order are obtainable in the alternating current, and the same frequencies are reproduced with regard to the impulses in the receiving instrument.

Certain structural improvements for efficient operation of the tube constitute other objects of the invention. Ordinarily, the current passed through the tube is concentrated in a line or band across the photo-electric surface. According to the present invention, the current is distributed more uniformly over the photo-electric surface.

This result is accomplished by forming the photoelectric surface on a conducting block of substantial thickness and establishing the current path through the block at a substantial distance from this surface, so that the current radiates to the surface with a fair degree of uniformity. Another structural improvement lies in the efficient transmission of the emitted currents from the current collector to the output post of the tube. Accordingly, the collector is so constructed that the side nearer its attachment to the output post is brought to a point from which connection is made to the output post. The current flowing from the collector is thus concentrated and directed toward the output post.

lhe invention is fully disclosed by way of example in the following description and in the accompanying drawing, in which- Figure 1 is a front elevation of the tube, partly in section;

Fig. 2 is a side elevation of the tube, partly in section;

Fig. 3 is a plan view of the tube, partly in section;

Fig. 4 is a vertical section of a modification, partly in section;

Fig. 5 is a front elevation, partly in section, of the tube shown in Figure 4; and

Fig. 6 is a side elevation, partly in section of another modification.

Reference to these views will now be made by use of like characters which are employed to designate corresponding parts throughout.

The tube is designed to be placed in the path of light beams to convert the same into electronic emissions and may be mounted for example, in back of a scanning disk of a television transmitter. The tube is enclosed within a suitable insulating housing 1 having an apertured flange 2 or equivalent means for attachment to a fixed part of the television apparatus. The housingl is lined with a heavy insulating material 3 which, if preferred, may be an integral part of the housing. Into the lining 3 is fitted a block 4 of high electrical conductivity, and in this connection, a uniform or pure metal is necessary to avoid lag and distortion. The exposed face of the block is retracted from the open side of the housing and liner, leaving an enclosed space 5 after the open 1 face is covered with a glass plate 6. This space is then evacuated. The plate consists of pressed glass having a grain perpendicular to the plane of the exposed face of the block 4, in order to avoid refraction and deflection of light to which the tube is exposed.

Before applying the plate 6, however, a fine wire screen 7 is stretched across the space 5, parallel to the face of the block and disposed between the space and the glass 6. Conductors 8 extend from the lower corners of the screen in a convergent manner towards a single conductor 9 embedded in the bottom side of the liner 3 and leading to a binding post 10 mounted in the bottom of the housing 1.

Binding posts 11 are passed through the opposite vertical sides of the housing and liner and into the block 4, in line with one anotherand removed as far as possible from the exposed face of the block. These posts are comprised in a high frequency alternating current circuit for the purpose and in the manner disclosed in the aforementioned co-pending application. The exposed face of the block is coated as at 12 with a photoelectric substance such as the sulphides or oxides of certain alkali metals. This substance is adapted to emit electrons when exposed to light and while the block l carries a negative charge of electricity. -The lateral wall of the space 5, around the liner 3, is coated with a material 13 which does not reflect rays of light, in order to avoid secondary emissions from the substance 12.

As already indicated, this tube is designed for use in conjunction with a receiving instrument wherein a film is developed by means of electrical discharges corresponding to the emissions from the tube. The production of electrical discharges in the receiving instrument requires interruption of the current, and according to the invention, the interruption is made directly at the tube rather than by means of an interrupting mechanism at the receiver, since the desired high frequency of interruption cannot be satisfactorily obtained by any known mechanical means. This end is accomplished in the present instance by the use of an alternating current flowing through the conducting block 4, inasmuch as there are no emissions While the current is positive, at

1 intermediate points of the screen are connected to the conductors 8 by fine wires 14 which may be continuations of the screen wires. The convergence of the collector to a point which is attached to the post 10 confines the flow of current to the post or, in other words,.provides a favored or easier path to the post. The emissions are converted into electrical impulses of the same frequency at the receiving set as fully disclosed in the aforementioned co-pend ing application. Not only may this frequency be of a very high order, corresponding to the available frequencies in alternating current, but therev is a time relationship or synchronism be opportunity to radiate from the line of the posts 11 to the coating 12 and thus spread over the latter. In the preferred construction, this distance is preferably equal to the length or breadth of the coated face, so thatthe conducting block is a cube 4 as shown in Fig. 6. This arrangement is to be distinguished from the ordinary case where the direct path of current is very close to the photo-electric surface, with the result that the current strength is highly concentrated at the current path.

- In the modification shown in Figures 4 and 5, the collecting medium consists of a gas-filled conducting space 5' rather than the screen. The space is lined with a conducting frame 15 which is thickened as at 16 at the side nearer the output post 10" and further caused to converge as at 17 to form a point which is attached to the thereof, according to the mounting of the scan- I ing medium in said space.

conductor 9 leading to the post 10'. Thus, as" in the previous construction there is provided a favored current path at the side of the collector near the output post and also concentration of the current path to the post. Any remaining exposed parts of the liner Wall at the space 5 are covered with a material 13 which is nonreflecting to light, as described in connection with Figure 2. The gas-filled tube is preferred because it avoids the obstruction introduced by a screen. 7

- In either construction, the favored current path and the output post are at the side of the tube which are in the direction of rotation of the scanning disk, and the alternating current is passed through the conducting block preferably in a line parallel to this side. Thus, the output post is not necessarily in the bottom of the tube but may as well be in one of the sides ningdisk and its direction of rotation, and in such case the posts 11 would be in the top and bottom of the tube.

Although specific embodiments of the invention have been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from thescope of the invention, as indicated by Y the appended claims.

What I claim is:

1. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a-photo-electric material on said face, conductors connected to said block at a substantial distance from said face, a conducting medium in advance of said face, a conductor extending from saidmedium and converging therefrom to a point, an output terminal, and a conductor connecting said point to said terminal.

2. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photoelectric material on said face, conductors connected to said block at a substantial distance from said face, ;an insulating casing enclosing said block and defining an enclosed space in front of said face, a conducting frame surrounding said face and insulated therefrom, and a gaseous conduct- 3. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photoelectric material on said face, conductors connected to said block at a substantial distance from said face, an insulating casing enclosingsaid block and defining an enclosed space in front of said face, a gaseous conducting medium in said space, a conductor extending from said medium and converging therefrom to a point,'an output terminal, and'a conductor connecting saidpoint to said terminal.

4. A photo-electric tube comprising a conducting block having an exposed face'and a substantial thickness behind said face, a photo-electric material on said face, conductors connected to said block at a substantial distancefrom said face, an insulating casing enclosing said block and,defining a laterally enclosed space in front of said face, a glass plate-applied to said casing in front of said face to seal said space, said tial thickness behind said face, a photo-electrical material on said face, conductors connected to said block at a substantial distance from said face, an insulating casing enclosing all except said face of said block, a conducting medium parallel to said face and supported by said casing, a glass plate applied to said casing parallel to said conducting medium and to said face, sealing said casing.

6. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photo-electrical material on said face, conductors connected to said block at a substantial distance from said face, an insulating casing enclosing all except said face of said block, a conducting medium parallel to said face and supported by said casing, a glass plate applied to said casing parallel to said conducting medium and to said face providing a sealed space therefor, said plate having a grain perpendicular to said face, said space being evacuated, and a conductor extending from said conducting medium.

7. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photo-electrical material on said face, conductors connected to said block at a substantial distance from said face, an insulating casing enclosing all except said face of said block, a conducting frame surrounding said face and supported by said casing, enclosing said block and defining a laterally enclosed space in front of said face, a glass plate applied to said casing parallel to said face to provide a sealed space therefor, a gaseous conducting medium in said space, and a conductor extending from said conducting space.

8. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photo-electric material on said face, conductors connected to said block at a substantial distance from said face, an insulating casing enclosing all except said face of said block and defining a laterally enclosed space in front of said face, a glass plateapplied to said casing in front of said face to seal said space, said plate having a grain perpendicular to said face, a conducting medium in said space, a conductor extending from said medium and converging therefrom to a point, an output terminal, and a conductor connecting said point to said terminal.

9. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photo-electric material on said face having an emitting surface responsive only to current of one sign for the emission of an interrupted current therefrom, conductors connected to said block at a substantial distance from said face, an insulating casing enclosing all except said face ofsaid block and defining a laterally enclosed space, a conducting frame surrounding said face and insulated therefrom, a glass plate applied to said casing in front of said face to seal said space, said plate having a grain perpendicular to said face, and a conducting medium in said space.

10. A photo-electric tube comprising a conducting block having an exposed face and a substantial thickness behind said face, a photo-electric material on said face having an emitting surface responsive only to current of one sign, for the emission of an interrupted current therefrom, conductors connected to .said block at a substantial distance from'said face for the application of an alternating current of the desired interruption frequency, an insulating casing enclosing all except said face of said block and defining a laterally enclosed space, a conducting medium disposed parallel to said emitting surface in said space, a conductor connected .to said conducting medium, a glass plate applied to said casing in front of said emitting surface to seal said space, said plate having a grain perpendicular to said face, and a vacuum in said space.

JOSEPH GE'I'IINGER. 

